U.S. Pat. Nos. 5,369,007, (hereinafter the '007 patent) and 5,200,321 (hereinafter the '321 patent), disclose a microassay on a card. In addition, a review of other devices and methods of microassay was provided in the '007 and '321 patents. The disclosure of those patents and the art cited therein is hereby incorporated by reference.
The '007 patent discloses a microassay card for detecting the presence of particular test substance in a liquid sample. The microassay card disclosed in the '007 patent consists of at least the following four functional layers of materials:
A. A paper label which can be eliminated if layer B has a printable or writable surface; PA1 B. A well contained within a hydrophobic layer for receipt of a liquid test sample; PA1 C. A supporting layer which is a substrate for a reagent that comprises either an anti-substance-enzyme conjugate bound to a substance which is immobilized on said layer or a substance-enzyme conjugate bound to an anti-substance which is immobilized on said layer; PA1 D. A semi-permeable layer which controls the rate at which the test solution is able to leave the upper layers and enter the bottom layer; PA1 E. A super-absorbent layer, which draws sample liquid down through the various layers of the device, containing a chromogenic substrate which changes color upon contact with either enzyme-conjugated antibody or enzyme-conjugated test substance released from the upper layers, depending on the nature of the moiety immobilized in layer C. PA1 Layer 1: An imprintable label; this layer may be absent if layer 2 is printable; only the printing needs to be changed for the upper card assembly to be used in the production of a microassay card having any desired specificity, as defined by layer 4 (see below). PA1 Layer 2: A plastic sheet. PA1 Layer 3: A high tack, pressure-sensitive adhesive layer having a removable covering. PA1 Layer 5: A plastic sheet. PA1 Layer 6: A semi-permeable membrane. PA1 Layer 7: A super-absorbent layer preferably containing a chromogenic enzyme substrate. PA1 Layer 8: A plastic sheet.
The instant disclosure provides a device and method similar in some respects to the device and method disclosed and claimed in the '007 patent. However, several novel features and improvements are provided herein such that the device of the instant invention is modular, in the sense that unitary portions of the device are separately manufactured and can be pre-assembled by the manufacturer for analysis of a particular analyte, or may be assembled in the field by the user, and thereby adapted for analysis of a wide range of analytes. In addition, because of novel features in the manufacture of the device of this invention, the reliability of the instant device is enhanced.
The '007 patent contains little disclosure about how the card can be manufactured and assembled. The disclosure concentrates on what is contained within each of the several layers. There is no teaching or suggestion of ways in which a particular device, once manufactured, could be modified to test for different substances based on the needs of the user. There is also no teaching or suggestion of a modular device which can be either pre-assembled or assembled in the field using highly reliable upper and lower card assemblies. Accordingly, from the disclosure of the '007 patent, one of ordinary skill in the art would understand that a different card would need to be specifically manufactured or purchased for each substance to be tested or each set of substances to be tested, or the card as purchased would need to have several wells, each pre-prepared for analysis of a particular test substance.